Field of the Invention
The present invention generally relates to suspension systems for prosthetic devices, and more particularly to vacuum pump systems for prosthetic limbs that include at least a mechanically activated pump.
Discussion of the Prior Art
Various systems have been developed for coupling a prosthetic device or prosthetic limb to a residual limb. The residual limb is connected to the prosthesis via a socket which receives and holds in place an end portion of the residual limb. Suspension is the mechanism that holds the socket to the residual limb. Vacuum is a form of suspension that uses a difference in atmospheric pressure to hold a socket to the residual limb. Liners help protect the residual limb tissue by providing cushioning and helping distribute the applied negative pressure in a uniform manner.
Vacuum pump technology is used to suspend the socket to the residual limb by creating a vacuum between the liner and the socket. The ability to maintain vacuum at a relatively consistent level can help avoid undesirable movement between the socket and the residual limb which improves comfort and avoids soft tissue damage.
Vacuum pumps fall into two categories, namely, mechanically activated or electrically activated. Electrically activated pumps tend to evacuate air more quickly, are able to monitor and adjust the vacuum pressure, and to automatically initiate pump operation if the vacuum pressure is not at least at a preselected threshold. However, electrically activated pumps include a small DC motor that requires a power source, such as disposable or rechargeable batteries. Electrically activated pumps also may generate undesirable noise.
Mechanically activated pumps use the walking motion of the user to create vacuum. One way pressure valves permit proper maintenance of vacuum pressure, without access to electricity. The necessary vacuum may be maintained indefinitely as long as there are no leaks in the system and/or the user walks occasionally. However, the mechanically activated pumps do not provide initial evacuation of air without effort, take longer to achieve operative vacuum levels, and typically need periodic motion to maintain appropriate vacuum levels. Mechanically activated pumps also tend to require a significant length for operation, as they typically operate by using a telescoping assembly. Depending on the number of parallel alignment elements involved, length can be important within a telescoping assembly, so as to provide adequate surface engagement to avoid binding. Mechanically activated pumps generally are configured for mounting below the knee because the pumps are too long to fit between the socket and the knee joint of the prosthetic limb, and as such, are not as well suited for transfemoral amputees.
Mechanically activated pumps also typically use a piston within a cylinder for pumping, or systems that include a flexible toroidal or ring-shaped reservoir or bladder that has a relatively large cylindrical telescopic tube running through the center, in place of a section of a lower limb pylon. The tube must be relatively large and of length sufficient to avoid binding, while withstanding the significant stresses encountered. In turn, the reservoir must be constructed to account for the large opening through the center.
For some users, such as military personnel with amputation who wish to return to active duty, there is an enhanced need to be able to maintain acceptable physical performance. An active soldier with amputation may be in the field for a prolonged period of time, with a need to maintain proper vacuum levels for suspension, while being without access to a power source for recharging of batteries. Thus, there exists a need for a compact, quiet, unobtrusive vacuum pump system with adjustable pressure and minimal battery recharging needs that will evacuate air from a cavity between a socket of a prosthetic limb and a residual limb.
The present invention addresses shortcomings in prior art vacuum pump systems for prosthetic limbs, while providing enhanced pumping systems that enable more flexible design and enhanced performance.